Process for manufacturing plates from wood shavings and fibers



June 8, 1965 u. GOTTSCHALK 3,188,367

PROCESS FOR MANUFACTURING PLATES FROM WOOD SHAVINGS AND FIBERS FiledSept. 28, 1961 United States Patent 3,188,367 PRQCESS Fill!MANUFAQTURING hLAZiES FREE/I W893) SHAVlNGS AND FEEERS UlrichGottschalh, Ludwigstrasse 1A, Jochgrim, Pfalz, Germany Filed Sept. 28,196i, ar. No.14i,491 Claims priority, application Germany, Sept. 3t),1966, G 39,614 7 Claims. (El. 264-37) The present invention relates to aprocess for manufacturing of plates from shavings and/or fibersespecially of wood by miXing these particles with a binder andsubjecting the mixture then to heat and pressure between the platens ofa press.

In known processes of manufacture of plates in this manner, the woodshavings and/ or fibers are first dried to a suitable degree, then mixedwith an appropriate binder and this mixture is placed in a substantiallyuniform layer between the platens of a press or in form of a pluralityof layers with sheet metal plates sandwiched therebetween, and then thelayer or layers are subjected in the press to appropriate pressurewhereby the press platens are preferably heated. The shavings are quiteoften treated with various chemicals and/or coloring agents before theyare subjected to heat and pressure so as to improve the quality of theobtained plates to make the same for instance resistant againsthumidity, to increase the flame resistance thereof, to make the platesresistant against attacl: by termites or to obtain plates of variouscolors. Part of the moisture contained in the material to be pressedevaporates during subjection of the material to heat and pressure. Thethus created vapor has to escape from the pressed layers during thepressing process to prevent bursting of the formed plates after releaseof the pressure, if the plates are not subjected to an expensive coolingprocess while the press remains closed so as to condense the vaporsbefore releasing the pressure. The necessary relatively high temperaturefor curing the binder will also cause part of the binder and anychemicals mixed with the shavings to evaporate and the odors of suchvapors may be disagreeably felt and lead also to an endangering of thehealth of the press operator. The water vapor and any other vaporsforming during the process can escape from the pressed layer or layersonly along the edges of the layer or layers since the main surfacesthereof are covered by the press platens or the sandwiched metal sheetsbetween a plurality of layers arranged between the press platens, whichdetrimentally increases the operating cycle.

During forming of a layer from the mixture of the shavings and binderand any other additions it is also rather difiicult to obtain a uniformdistribution of the mixture which will often result that the producedplates will have portions of different specific gravity. This mayproduce internal stresses in the pressed plates, causing in turn warpingof the same; This fact and the limited escape path for the vapors formedduring the pressing process, which escape through the edges of thepressed layers, render the production of pressed plates according to theknown processes rather difi'icult. This is especially true in theproduction of pressed plates of a thickness less than 8 millimeters,since with decreasing plate thickness, the specific pressure has to beincreased so that the escape of vapors through the edges of the pressedmateriallayer is rendered more difiicult and the time thereof isincreased, which in turn increases the pressing cycle. Thenecessary-high specific pressure for the production of plates of smallthickness results also some times in adherence of the shaviugs tothepressed plates. Furthermore any non-uniform distribution of theshavings and resulting non-uniform density in the plates willdetrimentalddfidfifi? Patented June 8, 1955 1y affect the shaperetaining quality of thin plates much more than that of heavier ones.These difiiculties increase especially the manufacturing cost of thinplates.

It is an object of the present invention to overcome these dirficultiesencountered in the manufacturing of pressed plates according to knownprocesses.

It is a further object of the present invention to facilitate escape ofvapors from the material to be pressed into plates during the pressingprocess and to reduce thereby the necessary operating cycle for formingsuch plates.

It is an additional object of the present invention to facilitate themanufacture of such pressed plates of substantially uniform specificweight so as to improve the quality of the obtained plates and so as tomake especially production of thin plates to a thickness of a minimum'of2 mm. commercially possible.

With these objects in view the process of manufacturing of plates fromshavings and fibers, especially of wood, comprises essentially the stepof mixing shavings and fibers of wood with a binder, forming at leastone layer of the binder treated material, superimposing upon said bindertreated material a second layer of moisture and vapor absorbingmaterial, and applying heat and pressure to said superimposed layers toform a plate from said binder treated material, whereby moisturecontained in said first mentioned layer and vapors forming during theprocess will be at least in part absorbed by the second layer. In otherwords, in the process according to the present invention moisturecontained in the binder treated material and vapors forming during theprocess cannot only escape through the edges of the layer of bindertreated material, but such moisture and vapors may escape through onemain surface of the binder treated material into the second layeradjacent thereto and in contact with this main surface so that thepressing cycle can be considerably reduced.

Preferably a pair of layers from said binder treated material with athird layer of moisture and vapor absorbing material sandwiched betweenthe pair of layers is arranged between the press platens so that twoplates can be simultaneously formed while moisture and vapors formingduring the process may escape from the outer layers of bindertreatedma-terial into the central layer of moisture and vapor absorbingmaterial.

Sincemost of the vapors produced during the process will be absorbed bythe central layer the escape of such vapors in the surroundingatmosphere is substantially prevented and any health damage produced bysuch vapors is thereby considerably reduced.

The central layer, according to the present invention is preferablyformed from resilient material so that with an uneven distribution ofthe material in the binder treated layers portions of the central layermay be compressed to a greater or lesser degree during the pressingwhich will result in an uneven surface of the finished 7 plates incontact withthe thirdlayer, while the finished The resilientintermediate layers can be formed frorn' various materials and the layermay be formed from continuous material or from loose particles.Especially in the first case it is preferred to treat the surfaces ofthe intermediate layer which come in contact with the binder treatedmaterial layers with material which is re;

pellent to the binder, or which at least will not adhere thereto, sothat an easy separation of the finished plates i from the intermediatelayer can be obtained. "Thus the surfaces of the intermediate layerwhich come in con- 3 tact with the binder treated material layers may bedusted with powdery material, or fabrics may be placed on the surfacesof the intermediate layer which come in contact with the binder treatedmaterial to prevent penetration of the binder into the intermediatelayer during the pressing process.

According to the present invention the intermediate layer may also beformed from wood shavings and fibers as are used for the outer layersfrom which during the pressing process the plates are formed, but thewood shavings and fibers for the intermediate layer are not mixed with abinder. The shavings and fibers which have served during the firstoperating cycle as intermediate layer and which have absorbed themoisture and vapors from the outer layers during the pressing process,are then mixed with a binder and used in the next press cycle forforming at least part of the outer lay-. ers from which the plates areto be formed. By properly choosing the volume of the intermediate layerit is possible to obtain in the intermediate layer during the pressingprocess and during transfer of the moisture content from the outerlayers into the intermediate layer, a moisture content in the.intermediate layer best suitable for mixing the material of theintermediate layer with the binder and for subsequent pressing of thethus obtained mixture into plates.

When the material of the intermediate layer is formed from wood shavingsand fibers which are subsequently used for forming part of the outerlayers from which the plates are to be formed, it is also possible tomix the shavings and fibers to be used as an intermediate layer, beforethey are introduced between the press platens with color additives, withmaterial to improve the flame resistance thereof, or other chemicals asmentioned above and such materials will penetrate into the shavingsand/or fibers during the limited heating of the intermediate layerduring the pressing process, substantially without evaporating. This mayalso increase the absorption capability of the surfaces of the woodshavings fibers for the binder material to be mixed subsequent withthese shavings and the chemicals which have been absorbed by theshavings and fibers of the intermediate layer will be rendered lessvolatile during the subsequent pressing process.

According to known processes it is preferred to compress the bindertreated material in a third or quarter of the total press cycle with themaximum pressure to the desired finished plate thickness and to reducethereafter the pressure in steps or gradually up to the end of thepressing cycle. Contrary to this usually used pressure cycle it ispreferred according to the present invention to gradually increase thepressure from the start to the end of the pressing cycle or to graduallyincrease the pressure upto the maximum pressure necessaryto obtain thedesired plate thickness at the start of the pressing cycle and tomaintain the maximum pressure then up to the end of the pressing cycle.

If spacer means are used in a known manner to limit the approach of thepress platens to each other to a predetermined degree, it is preferredaccording to the present invention to increase the pressure on the pressplatens gradually so that the press platens will abut against the spacermeans only at the end of the operating cycle.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appendedclaims. Theinvention itself, together with additional objects and advantagesthereof, will be best understood from the following description of aspecific method when read in connection with the accompanying drawingwhich schematically illustrates an arrangement for carrying out themethod of the present invention.

The drawing schematically illustrates a novel arrangement of knownapparatus and machine elements with l respect to each other and noattempt has been made to illustrate the specific construction of thevarious apparatus used, since such apparatus are well known in the artand the specific construction thereof does not form part of the presentinvention.

According to the arrangement shown wood in the form of blocks or logs isfed into a shaver or comminuting means 1 to be comminuted therein intowood shav ings and/or fibers and the wood particles produced in thecomminuting means 1 have to be made the smaller the thinner thethickness of the produced plate is to be. If the thickness of theproduced plate is to be smaller than 5 mm., it is preferred to comminuteat least part of the wood into fibers and the percentage of wood fibersto wood shavings, has to be increased the thinner the produced plate isto be. The shavings and/ or fibers produced in the comminuting means 1are then transported by transporting means, schematically illustrated bythe arrow, into a drier 2 in which during the first operating cycle partof the material is dried to a lesser and another part is dried to ahigher degree. The lesser dried fibers and/or shavings are thentransported over the path a by transporting means of known constructionsinto mixing means 3 of known construction in which the shavings and/ orfibers are mixed with a binder. The binder treated material is fed bythird transporting means, schematically shown in the drawing, betweenthe platens 7 of a press 6 while the portion of the shavings and/orfibers dried to a higher degree in the dryer 2 is fed over thepath b bya fourth transporting means between the press platens 7 to form anintermediate layer 5 between the layers 4 formed by the binder treatedmaterial. The press platens 7 are preferably heated and the superimposedlayers 4, 5, 4 are then subjected to pressure by moving the pressplatens 7 toward each other. During application of heat and pressure tothe superimposed layers the binder material is cured whereby moistureand vapor emanating from the material of the layers 4 will besubstantially absorbed by the shavings and/or fibers of the intermediatelayer 5. The pair of plates 4, 4' produced from the layers 4 areseparated at the end of the press cycle from the intermediate layer 5and subsequently transported over the path 0 by transporting means ofany well known construction into a brushing apparatus 8 which has a pairof brush rollers 8, 8" for brushing any shavings and/or fibers of theintermediate layer 5, adhering to the finished plates, therefrom. Thebrush rollers 8' and 8" are preferably shiftable in vertical directionso that only the surface of the respective plate 4 which was during thepressing process in contact with the intermediate layer 5 will bebrushed off during the passage of the respective plate through thebrushing means 8. Preferably, the plates 4', 4 are subsequently passedthrough a planer 9 which has a pair of rotating planers 9', 9", whichare also preferably shiftable in vertical direction so that duringpassage of the respective plates 4' through the planer 9 only suchsurfaces of the plates will be machined which have been during thepressing operation in contact with the intermediate layer 5.

The shavings and/or fibers of the intermediatelayer 5, the humiditycontent of which has been increased during the preceding pressingprocess to a degree suitable for the subsequent application of a binderand press forming the material into plates, are transported after thefirst pressing cycle over the path d, by transport ing means of any wellknown construction, into the mixing means 3 in which this material ismixed with a binder, so that the mixture may be subsequently used forforming at least part of the layers 4 between the press platens, to beformed during the next pressing cycle into plates 4. Before feeding thematerial of the intermediate layer 5 into the mixing means 3, thecompressed shavings and/or fibers may be loosened up by any means isknown in the art. The shavings and/or fibers removed from the finishedplates 4' in the apparatus 8 and the shavings produced during machiningof the finished plates 4' in the apparatus 9 are preferably also fedtogether with the material of the intermediate layer into the mixingmeans 3 to be mixed with the binder so that any waste of material isavoided.

By properly selecting the volume of the shavings and/or fibers of thelayers 4 and the intermediate layer 5 it is possible, after the firstmolding cycle, to use the material of the intermediate layer 5 to formtherefrom part or all of the outer layers 4 from which the plates are tobe formed so as to omit feeding of lesser dried shavings and/or fibersfrom the dryer 2 over the path a into the mixing means 3, or toconsiderably reduce the amount of shavings and/or fibers fed over thispath. In other words, during the second and following pressing cycles,the material used in the preceding pressing cycle to form theintermediate layer 5, is mixed with a binder and the thus obtainedmixture is then used for forming the layers which are subsequentlyformed into the plates 4'.

If the plates to be produced are to be provided with special additives,such as paraifin and mineral waxes to increase the moisture resistanceof the finished plates, or ammonium phosphate or boric acid as flameresisting agents, pentachlorophenol to prevent attack of the finishedplates by termites, or any color additives, then such additives orchemicals are preferably mixed in an additional mixer to the shavingsand/or fibers which are first used for forming the intermediate layer 5.In this way such additives or chemicals will penetrate the shavingsand/or fibers forming the intermediate layer 5 during the pressingprocess, whereby better action of these chemicals and additives on thematerial is obtained.

If the intermediate layer 5 is not formed from loose shavings and/orfibers, but from continuous but resilient material, then it is preferredto cover the surfaces of the intermediate layer 5 in contact with theouter layers 4 with powdery material which will substantially preventpenetration of the binder material of the layers into the intermediatelayer 5 so as to facilitate separation of the intermediate layer fromthe plates 4' formed from the outer layers 4. For the same purpose thesurfaces of the intermediate layer 5 in contact with the outer layers 4may also be covered with netlike material or fabric permeable bymoisture and vapor.

The pressure on the plates 7 of the press is preferably controlled asmentioned above, that is, the pressure is either increased graduallyfrom the beginning up to the end of the press cycle, or the pressure isincreased during the beginning of the press cycle to the necessarymaximum, to obtain the desired plate thickness and then maintained atthis maximum up to the end of the pressing cycle. If spacer means areused between the press platens to limit the extent of approach thereofto each other, then the pressure is controlled in such a manner that thepress platens will contact the spacer means only at the end of the presscycle.

It is understood that the process of the present invention can becarried out with more than three layers and in this case an intermediatelayer 5 formed from material as mentioned above is always placed betweentwo subsequent layers 4 from which the finished plates 4' are to beformed.

While the invention has been illustrated and described as embodied in aprocess for manufacturing of pressed plates, it is not intended to belimited to the details shown, since various modifications many be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can ous applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention and, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A process of manufacturing plates from wood shavings and fiberscomprising the steps of mixing wood shavings and fibers with a binder;forming a pair of layers from said binder treated material with a thirdlayer of Wood shavings and fibers without a binder sandwichedtherebetween; applying heat and pressure to said superimposed layers toform a pair of plates from said layers of binder treated material,whereby moisture contained in said pair of layers and vapors formingduring the proc ess will be at least in part absorbed by said thirdlayer; separating said plates from said third layer; mixing the materialof said third layer with a binder; and using the thus obtained mixturefor forming at least part of a pair of layers for forming platestherefrom during the next operating cycle.

2. A method as defined in claim 1 in which said wood shavings and fibersfor forming the third layers are mixed with material for increasing themoisture resistance thereof.

3. A method as defined in claim 1 in which said wood shavings and fibersfor forming the third layers are mixed with material for increasing theflame resistance thereof.

4. A method as definedin claim 1 in which said wood shavings and fibersfor forming the third layers are mixed with material forpreventingattack of the finished plates by termites.

5. A method as defined in claim 1 in which said wood thus obtainedmaterial to reduce the moisture contents thereof to a predetermineddegree suitable for mixing the material with a binder; drying anotherportion of said comminuted wood material to a greater degree than saidfirst mentioned portion; mixing said first mentioned portion of saiddried material with a binder; forming from said binder treated materiala pair of layers and from said second mentioned portion a third layersandwiched between said pair of layers; subjecting said superimposedlayers to heat and pressure to form a pair of plates from said bindertreated layers, whereby moisture contained in said pair of layers andvapors forming during the process will be at least in part absorbed bysaid third layer and said third layer being made of such a thicknessthat the moisture transferred thereinto will moisten the material ofsaid third layer to contain a degree of moisture substantially equal tosaid predetermined degree; separating said plates from said third layer;mixingthe material of said third layer with the binder; and using thethus obtained mixture for forming at least part of a pair of layers forforming plates therefrom during the next operating cycle. i

7. A process of manufacturing plates from wood shavings and fibers,comprising the steps of mixing said shavings and fibers with a binder;forming -a pair of layers from said binder treated material with a thirdresilient layer of particulated moisture and vapor absorbing materialwithout a binder sandwiched between said pair of layers; applying heatand pressure to said-superimposed layers to form a pair of plates fromsaid binder'treated material, whereby moisture contained in said pair oflayers and vapors forming during the process will be at least in partabsorbed by said third layer; separating said plates from said thirdlayer; brushing any particles of "1 8 ing said plates after separationat surfaces thereof which 2,431,720 12/47 Willey. had been directedtoward said third layer; mixing said 2,587,171 2/52 Knewstubb et a1156-254 brushed-01f particles, the shavings obtained in the plan-2,642,371 6/53 Fahrni 15632 ing operation and the material of said thirdlayer with 2,745,779 5/56 Ritter et al. 154-45.9 a binder; and using thethus obtained mixture for form- 5 2,322,028 2/58 flimmelheber et 1 15636 ing at least part of a pair of layers for forming plates 3 057,022 102 Bar et 1 2 4 113 th f d th t t' r l ere r0111 uring e nex opera ing(:36 e FOREIGN PATENTS References Cited by the Examine-1' 401,553 11/33Great Britain UNITED STATES PATENTS 10 v T 5 5 7 /02 Edison ALEXABDERODMERKEL, Przmary Examiner.

1,098,967 6/14 Peterson 156-323 EARL M. BERGERT, Examiner.

1. A PROCESS OF MANUFACTURING PLATES FROM WOOD SHAVINGS AND FIBERSCOMPRISING THE STEPS OF MIXING WOOD SHAVINGS AND FIBERS WITH A BINDER;FORMING A PAIR OF LAYERS FROM SAID BINDER TREATED MATERIAL WITH A THIRDLAYER OF WOOD SHAVINGS AND FIBERS WITHOUT A BINDER SANDWICHEDTHEREBETWEEN; APPLYING HEAT AND PRESSURE TO SAID SUPERIMPOSED LAYERS TOFORM A PAIR OF PLATES FROM SAID LAYERS OF BINDER TREATED MATERIAL,WHEREBY MOISTURE CONTAINED IN SAID PAIR OF LAYERS AND VAPORS FORMINGDURING THE PROCESS WILL BE AT LEAST IN PART ABSORBED BY SAID THIRDLAYER; SEPARATING SAID PLATES FROM SAID THIRD LAYER; MIXING THE MATERIALOF SAID THIRD LAYER WITH A BINDER; AND USING THE THUS OBTAINED MIXTUREFOR FORMING AT LEAST PART OF A PAIR OF LAYERS FOR FORMING PLATESTHEREFROM DURING THE NEXT OPERATING CYCLE.